Refactoring

I've moved quite a lot of code into separate packages for the sake of
clarity. Also did some reformatting.

Currently we have these packages:

    rest
    ├── auth            # user-related models
    ├── base            # base routes (static files, 404)
    ├── tasks           # tasks-related functionality
    ├── db              # db configuration and migrations
    └── core.clj        # ties together the routes and defines the app

I also deleted the `sql` folder since it wasn't used anymore.